This invention relates to substrates for electronic circuit boards, and has particular relation to multilayer circuit boards containing an organic layer and an inorganic layer, such as ceramic.
Ceramic has many advantages over organic materials when being used as a circuit board substrate. Its coefficient of thermal expansion more closely approximates that of the chips which are to be bonded to the substrate, and it allows a greater density of chips to be bonded to the substrate. However, it is both expensive and difficult to work, especially to drill holes in. Organic substrates are both cheap and easy to drill. It is therefore desirable to combine the advantages of both organic and inorganic substrates into a hybrid substrate, while avoiding the disadvantages of each.